Auditory evoked potentials in suspected idiopathic normal pressure hydrocephalus: longitudinal associations with tap test and clinical outcomes.

New biomarkers are needed to improve the clinical profile of idiopathic normal pressure hydrocephalus (iNPH), a potentially reversible cause of cognitive and functional decline in older adults. The Tap Test (TT) is commonly used to support clinical decision-making regarding ventriculoperitoneal shunt (VPS) surgery; however, objective markers of treatment response remain limited. This study aimed to investigate whether auditory brainstem response (ABR) and cortical auditory evoked potentials (CAEP) measures are associated with clinical response to the TT and with longitudinal clinical outcomes in older adults with suspected iNPH. Fifty-five older adults (mean age: 75 ± 7.04 years) were evaluated before and after lumbar puncture and during follow-up (3-12 months). Participants were categorized into three clinical outcome groups: TT-negative without VPS, TT-positive without VPS, and those who underwent VPS. Clinical assessment included gait and neuropsychological testing, while neurophysiological evaluation comprised ABR and CAEP. A high prevalence of previously undiagnosed hearing loss highlighted the importance of systematic audiological assessment in this population, given its potential impact on cognition and functional outcomes. ABR abnormalities were frequent but not associated with clinical changes. CAEP did not reflect response to lumbar puncture during the TT. However, shorter P1 latencies were associated with better gait performance, and reduced P2 latency after VPS may reflect improved cortical processing. CAEP measures, particularly P1 and P2 latencies, represent a potential candidate marker for monitoring postoperative improvement in older adults with iNPH; however, this requires further validation in future studies.